I think I might have found the sound I'm looking for, or at least something close to it. I was previously using the updated version of the RP2 mods with the 840 pads, sometimes referred to as RP2i.
I'm no basshead, but I do like perhaps a bit more bass and warmth in my sound than most would call completely neutral. Why? I have a 12" subwoofer in my car and a nice 8" one for my stereo setup, so I'm used to plenty of sub-bass and punch. Headphones have a difficult time replicating that, and even if they measure out neutral with good bass extension, it's usually just not the same. For example, I found the stock D2000 to be slightly bloated and boomy, but I found the HD598 to be slightly bass-light. Somewhere in between there is a sweet spot for me, but probably closer to the D2000 than the HD598. I also just happen to prefer a bit of warmth in my sound. I like the life and fullness it brings to the sound.
I also don't like how many headphones seem to artificially brighten the sound. I specifically use silk-domed tweeters in my car and home stereo setups because they are smoother sounding than, say, aluminum tweeters. Some might consider them to be lacking in detail, but my ears say otherwise. It's a lot like the exaggerated sharpness on most TVs you buy. When sharpness is set where it's actually supposed to be, the picture might seem less clear at first. Once you adjust to it, you realize that you're seeing the details as they are without any artificial sharpening. That's what a lot of headphones sound like to my ears. I also seem to be sensitive to brightness and sibilance.
How did the 840 RP2i mods work out for me? Really well, actually. I was just wishing I could get a bit more bass response out of them. I wanted some extra warmth, heft, dynamics, and lushness in my sound. And while it was completely listenable and enjoyable, I found the treble perhaps too bright at times. The key changes I made were removing the stuffing from the back of the 840 pads and getting rid of the reflex dot (duct tape, in my case) from the the back of the driver. In fact, the back of the driver had nothing covering it. No felt, no tape, just naked. With 6 regular sized cotton balls teased and stuffed in the cans, they sound fine naked (to my ears).
I found that I did not like how the stuffed 840 pads sounded. The stuffed pads did seem to add some favorable aspects to the sound in the mids, soundstage, and imaging, but they also seemed to reduce the bass warmth. I did some A/B comparisons, and sure enough, the sound was much more lush and full without anything raising up the back of the earpads. In some ways, they seem more 2D now, but I found the soundstage and imaging to be more than adequate. I mean, I'm used to bookshelf speakers and a dedicated subwoofer...Headphones are almost always disappointing in that area in comparison.
Removing the duct tape from the back center of the driver also brought out the bass a bit more and helped smooth out the treble into something quite detailed without much in the way of excessive brightness. I had to close up the vents a bit more to compensate for the extra bloat it brought to the upper bass and lower mids.
While they seem to extend deeper, have more bass, and have smoother treble than before, they still aren't perfect sounding. At times, the bass does ever so slightly unruly and bloated for my tastes, and the mids might not be perfect in all ways. Hard to say, because my ears aren't perfect either. I am hearing more sub-bass though, and I do like that. Overall, I'm really digging them, but I'll probably end up messing with them again for fun. All I know is that a perfectly neutral, analytical sound is not completely what I'm looking for. It's a mixture of neutrality and my own personal tastes.
Anyway, just to make things simple, here's a complete list of my mods. Perhaps someone will find these helpful:
1. Silverstone acoustic foam completely lining the cups (cut neatly, no draping, maximizing volume)
2. Felt removed from cup vents, covered all but the bottom slit in Silverstone acoustic foam. Leave that bottom vent slit open (covering it in cotton, step 3, is recommended)!
3. Filled the cups with 6 regular sized cotton balls (medical grade from CVS, if it matters). I completely teased these apart before stuffing the cups. It needs to be uniform, and it needs to cover everything, including the center post (which is covered in acoustic foam) and vent area.
4. Plasticine in the back of the driver baffle
5. Silverstone acoustic foam covering most of the plasticine
6. Nothing on the back of the drivers. No felt (stock or otherwise), no reflex dots. Nothing.
7. Felt removed from the ear-side baffle (keep protective mesh in front of driver), and just one layer of Silverstone acoustic foam covering the entire ear-side baffle. Leave openings for the screw holes, EQ hole, and, obviously, the driver.
8. 840 earpads. No stuffing in the backs or anything like that.
9. Cover the 3 vents you closed off inside with duct tape or electrical tape on the outside of the cups. For the bottom, open vent, cover about 75% of that with your tape. You can tweak that to your liking. In fact, you might want to consider placing acoustic foam on the inside of the cups to cover up as much of the bottom vent as you like.
Edited by hans030390 - 11/29/11 at 12:45am